57) What is the area of circle which passes through all the corners of a square of side 8 cm?

58) Following spindle speeds (in RPM) are available in a drilling machine - 100, 200, 400 and 800. For drilling Dia 20 mm hole in mild steel plate, at cutting speed 30 m/min, what is the preferred RPM to run the machine?

59) While horizontal aligning of a machine bed of 3 m length, spirit level of sensitivity 0.2 mm/m show a deflection of 4 graduations. Shim thickness required to be placed underneath to make the bed horizontal is

60) What is the approximate cutting speed (in mm/minute) for turning dia 30 mm shaft, if spindle rotates at 300 RPM?

61) Determine the height of slip gauges if a sine bar (200 mm length) makes and angle of 30 degree